/* ocss  面向对象的 css 编程 */
.btn {
    width: 100px;
    height: 50px;
    background: #fff;
    color: black;
    border: none;
    border-radius: 10px;
    border: 1px solid #ccc;
    margin: 10px;
}
.btn.btn-primary {
    background: green;
    color: white;
    border: none;
}
.btn-lg {
    width: 200px;
    height: 100px;
}
.btn.btn-info {
    background: blue;
    color: white;
    border: none;
}
.btn.btn-danger {
    background: red;
    color: white;
    border: none;
}
.btn.btn-warning {
    background: orange;
    color: white;
    border: none;
}